CVE-2025-66038: opensc_project opensc Buffer Over-read

Vulnerability summary

CVE-2025-66038 is a medium (CVSS 6.8) Buffer Over-read vulnerability in opensc_project opensc. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 19.4% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 30-03-2026
   PublishedVulnerability first disclosed.
2. 01-04-2026
   Last modifiedVulnerability information updated.

Description

OpenSC is an open source smart card tools and middleware. Prior to version 0.27.0, sc_compacttlv_find_tag searches a compact-TLV buffer for a given tag. In compact-TLV, a single byte encodes the tag (high nibble) and value length (low nibble). With a 1-byte buffer {0x0A}, the encoded element claims tag=0 and length=10 but no value bytes follow. Calling sc_compacttlv_find_tag with search tag 0x00 returns a pointer equal to buf+1 and outlen=10 without verifying that the claimed value length fits within the remaining buffer. In cases where the sc_compacttlv_find_tag is provided untrusted data (such as being read from cards/files), attackers may be able to influence it to return out-of-bounds pointers leading to downstream memory corruption when subsequent code tries to dereference the pointer. This issue has been patched in version 0.27.0.

• CWE-126Buffer Over-readThe product reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.